It is well known to immobilize two vertebrae relative to each other using an intervertebral implant in a rigid material, forming a cage which defines a housing, this housing being intended to receive one or several bone grafts and/or cancellous bone shavings. The implant makes it possible to reestablish suitable spacing of the vertebrae and to prevent crushing of the graft(s) by the said vertebrae. The vertebrae are immobilized relative to the implant by growth of bone cells through the graft(s) and/or shavings, leading to what is commonly called a “fusion” of two vertebrae.
Certain intervertebral implants have a reduced width, enabling their placement from the rear, on both sides of the spinal cord. It is then necessary to place two implants, one on the left side of the spinal cord and the other on the right side.
This technique has the drawbacks of being relatively risky to implement, involving the piercing of holes near the spinal cord, requiring the use of hollow implants with a reduced width, allowing only a small contact surface of the grafts with the vertebrae, and not being usable on spinal vertebrae, for reasons related to anatomy.
To resolve these drawbacks, it is common to place an intervertebral implant from the front. The approach being larger than from the rear, such an implant can have a shape such that it extends over a major part of the surface of the vertebral plate, and can therefore contain one or several grafts having a significant contact surface with the vertebral plates, which is an essential condition for the success of the vertebral fusion. An implant of this type comprises a peripheral wall defining said housing and one or several internal partitions making it possible to strengthen its structure so that it can bear the stresses exerted on it during its impaction between the vertebrae.
This type of implant, largely used in practice, is not, however, fully satisfactory with regard to the vertebral fusion obtained.
Document US 2007/016295 describes an implant comprising two elongated elements with a reduced width, defining, at the level of their edges, two longitudinal surfaces opposite each other, these elements being intended to be positioned between the vertebral plates of the vertebrae, away from each other, with their longitudinal surfaces in contact with the vertebral plates.
The shaping of these implants does not, however, make it possible to achieve the objectives of being able to be easily introduced into the intervertebral space, being able to be arranged optimally in this space and being able to be maintained in a suitable position in this space.
Documents U.S. Pat. No. 5,397,364, EP1752116A1 and U.S. Pat. No. 6,656,178 describe different types of implants which do not make it possible to resolve the aforementioned drawbacks.